Circuit element



Oct. 3 1967 G. LUTZ 3,345,598

CIRCUIT ELEMENT Filed April 26, 1965 INVENTOR Georg Lutz ATTOR NEYS 3,345,598 CIRCUIT ELEMENT Georg Lutz, Nurnberg, Germany, assignor to Telefunlcen Patentverwertungs-G.rn.b.H., Ulm (Danube), Germany Filed Apr. 26, 1965, Ser. No. 450,713 priority, application Germany, Apr. 25, 1964,

4 Claims. of. 338-415 Claims ABSTRACT OF THE DISCLOSURE An electrical resistor including an elongated support body having a non-circular and non-square cross-sectional configuration with a bifilarly disposed layer of resistance material on the support body defining a resistance path whose end portions are located on opposing sides of the same end of the support body. A metal contact layer is disposed on each of the end portions of the resistance path,

:and the opposite sides on the end of the support body adjacent'the contact layers are laterally beveled between the end portions of the resistance path to provide for ease .in positioning the body in an opening on a printed circuit :board.

, Y The present invention relates generally to the electrical component art and, more particularly, to an electrical resistor and to a method for producing such an electrical .resistor for use in printed circuits, in which a resistance layer is applied bifilarly on a rounded elongate insulator body and the connections or terminals are provided at one end.

In such a resistor'of conventional type, the connection wires on one side of a small plate-like carrier are connected to the ends of the resistor which is formed on one side surface of the plate in meander fashion and lead through the small plate to the opposite side. It is also .known to lead the wires out at the same side, in which case these wires are-connected to the resistor ends on the resistance layer and, at first, extend into the interior present invention wherein the insulator body is at first covered with the insulation layer, if necessary with the exception of one end to provide an adjacent short exposed length of resistance layer, and either before or after this, one end, such as the end with the adjacent short sheath or exposed length which does not have an insulation layer is metallized so as to be capable of being soldered. Then the surface that is metallized so as to be solderable is separated into two zones and the resistance layer is separated into two resistance paths in such manner that each solderably metallized zone is connected to one resistance path and the two resistance paths are connected to each other in an electrically conductive manner via the opposite end or, if necessary, via an adjacent sheath length.

This provides the advantage, compared to conventional small plate-like insertable resistors, that the resistor body can be produced in a manner which is conventional for layer resistors by deposition of a resistance layer on a carrier and successive grinding-in of a groove with simul- United States Patent 3,345,598 Patented Oct. 3, 1967 taneous resistance adjusting or balancing, whereas the con ventional insertable resistors can be produced only by vaporization, spraying or printing. The last-mentioned production methods are, however, too expensive and time consuming when a high degree of accuracy is required, and when production is technically very simple, only a very low degree of accuracy is provided. Furthermore,

no special cont-act mounting procedures are necessary in .circuit board.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a bottom view of the present invention.

FIGURE 2 is a partial sectional view of the embodiment of FIGURE 1 shown mounted in a circuit board.

FIGURE 3 is a bottom view of another embodiment of the invention.

FIGURE 4 is a partial sectional view of the shown in FIGURE 3.

I FIGURE 5 is a partial sectional view of the embodiment shown in FIGURE 3 but considered at a right angle from the view of FIGURE 4.

' With more particular reference to the drawings, FIG- URES 1 and 2 show an electric-ally insulating carrier body 1 which is covered with a layer of resistance material 2. The resistance layer 2 is preferably a pyrolytically deposited carbon layer. It can, however, also be a met-a1 layer or a metal layer applied-in addition to the carbon layer-which is applied by vaporization, spraying or chem- .ically or'electrochemically.

A suitable ceramic material preferably serves as the carrier body. In a suitable coating procedure, a plastic material can be used which can withstand the soldering temperature, at least for a short time, like carbon polytetrafiuoride, polyethylene, polypropylene, etc.

The separation of the resistance layer 2 into a spiral is performed according to the invention by grinding in a wound coil 3, 4. This provides the resistance paths 5, 6, whose ends remain in connection with each other at the upper end 7 of the carrier body 1. In the case of a resistance layer 2 which is applied by imprinting, vaporizing or spraying, this layer can be applied in a wound coil shape with separated initial portions and connected ends, so that grinding is no longer necessary or only necessary for adjusting or balancing.

At the lower carrier end 8, the resistance layer 2 is completely separated so that the ends 9, 10, of the resistance paths 5 and 6 form the beginning and the end of the resistance wound coil. The ends 9, 10, are metallized with a material which can be soldered, especially when the resistance layer 2 is not itself capable of being soldered.

The resistor body is coated with a protection coating 11, made for example of lacquer or plastic and extending to the beginning of the metallized portion. The lacquer layer can advantageously serve to prevent the structural element from slipping through the insertion opening. This coating is preferably not only an electrical insulator but is moisture proof as well to protect the resistor.

When inserting the resistor into a printed circuit board 12, the ends 9 and 10 extend through an opening 12 which corresponds to the cross section of the carrier end 8, and can there be soldered to the conductors 13, for example by dip soldering.

FIGURES 3, 4 and 5 show a similar resistor whose cross one embodiment of embodiment section is at least generally elliptical. Similar parts are designated with similar reference numerals, but with primes added. The separation of the metal layer at the lower end is here made by laterally obliquely grinding off two mutually opposite edge zones 14, 15. The oblique formation makes it possible to insert the structural element in a self-locking manner into the correspondingly designed hole and then to solder it in. This embodiment can also be applied when using round or other cross sections.

The entire lower surface 8' can advantageously be freed from the resistance layer and/or the metallized portion by grinding off these surfaces. Under certain circumstances, for example, at higher voltages this is advantageous. It is also advantageous during the soldering process because the formation of a solder bridge can not take place so easily.

The use of an elliptical cross section or of a carrier body that has outer surfaces that have planar parallel sides and half-round ends, has the advantage, compared to the round cross section, that this form can serve for aiding proper orientation during grinding or the applying of the'wound coil and for placing these elements into the circuit boards. This form or shape can furthermore be stacked more easily, and, on the other hand, can still be processed'by the plain griding method.

In order to obtain proper orientation in the embodiment having a round cross section, a slot can be provided in the carrier body or a projection or another kind of marking, on the basis of which the beginning or initial portion of the wound coil can clearly be determined relative to the contact portions and especially relative to the flattened edge zones 14, 15, which may be present.

The resistor of the present invention can, for example, be produced as follows. A carrier body 1 made of ceramic is provided with a hard carbon layer that is deposited from the gas phase in an oven at a temperature of about 900 to 1100 C. After this, one end of each body is metallized galvanically or chemically so as to be capable of being soldered. Then, the wound coil is ground in and the metallized portion separated. The separation is suitably performed by abrading the metallized portion from the end 8 and by a lateral abrading of at least the metallized portion, for example, the metallized portion of the edge zones -14, 15, inthe area of the beginning of the ground in wound coils 3 and 4. After this, one or more coatings of lacquer are used to provide the resistance layer. The lacquer layer can be relatively thick so that it prevents the resistor from slipping through the opening in the circuit plate. Such slipping through is, however, preferably prevented by the obliquely ground off edge portions 14, 15.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. An electrical resistor comprising, in combination:

(a) an elongated support body of insulating material,

at least one end of said support body having a noncircular and non-square cross-sectional configuration;

(b) a bifilarly disposed layer of resistance material on said support body, said layer of resistance material being disposed in a continuous resistance path whose two end portions are located on opposing sides of said support body at said one end thereof;

(c) a metallic contact layer on each of the end portions of said resistance path; and

(d) the portions of said support body which lie between the two end portions of said resistance path being laterally beveled at said one end of said support body.

2. An electrical resistor as defined in claim 1 wherein said one end of said support body has an elliptical crosssectional configuration.

3. An electrical resistor as defined in claim 1 wherein said resistor is covered with a moisture-proof coating of insulating material except in the area of said metallic cont act layers.

4. An electrical resistor as defined in claim 3, wherein said supporting body is dimensioned to be inserted at said one end thereof into an opening in a plate, and wherein said coating of insulating material is thick enough to act as an abutment preventing the supporting body from sliding entirely through the opening in said plate.

References Cited UNITED STATES PATENTS 1,681,956 8/1928 Shriner 338265 X 1,972,162 9/1934 Parrott 338-265 X 2,367,570 1/ 1945 Funarolf 3383 00 X 2,503,418 4/1950 Scramton 338300 X RICHARD M. WOOD, Primary Examiner.

J. G. SMITH, Assistant Examiner. 

1. AN ELECTRICAL RESISTOR COMPRISING, IN COMBINATION: (A) AN ELONGATED SUPPORT BODY OF INSULATING MATERIAL, AT LEAST ONE END OF SAID SUPPORT BODY HAVING A NONCIRCULAR AND NON-SQUARE CROSS-SECTIONAL CONFIGURATION; (B) A BIFILARLY DISPOSED LAYER OF RESISTANCE MATERIAL ON SAID SUPPORT BODY, SAID LAYER OF RESISTANCE MATERIAL BEING DISPOSED IN A CONTINUOUS RESISTANCE PATH WHOSE TWO END PORTIONS ARE LOCATED ON OPPOSING SIDES OF SAID SUPPORT BODY AT SAID ONE END THEREOF; (C) A METALLIC CONTACT LAYER ON EACH OF THE END PORTIONS OF SAID RESISTANCE PATH; AND (D) THE PORTIONS OF SAID SUPPORT BODY WHICH LIE BETWEEN THE TWO END PORTIONS OF SAID RESISTANCE PATH BEING LATERALLY BEVELED AT SAID ONE END OF SAID SUPPORT BODY. 